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The following points highlight the two major diseases caused by tapeworms. The human diseases are: 1. Taeniasis 2. Echinococcosis.
Human Disease # 1. Taeniasis:
Taeniasis is caused by the species belonging to the genus Taenia, which include mainly T. solium (pork tapeworm) and T. saginata (beef tapeworm). Man acquires the infection by eating raw or under-cooked pork or beef that contains the cysticerci. The cysticerci develop into adult tapeworms in the intestine of man.
The presence of tapeworms in the intestine causes gastro-intestinal disorders. Occasionally they may be responsible for vague abdominal discomfort, chronic indigestion, anaemia and intestinal disorders such as diarrhoea alternating with constipation. Anaemic conditions may also develop.
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Diagnosis may be made by stool examination for segments and eggs of the tapeworm. The drug of choice is mepacrine (Atebrin). Other antihelminthic drugs are dichlorophen and yomesan, a chlorosalicylamide derivative (for Taenia segments).
Human Disease # 2. Echinococcosis (Hydatid Cyst):
Echinococcosis is an infection caused by larval cestode, hydatid worm of Echinococcus granulosus. The definitive hosts of this tapeworm are dog, wolf, fox and jackal. The eggs of this tapeworm are set free in the intestine of the definitive host.
The eggs are released in the faeces and develop into onchospheres. Man acquires infection on eating food or drinking water contaminated with onchosphere-containing eggs. Larvae released from the eggs penetrate the wall of the gut, enter the blood stream and disseminate to deep organs such as liver, lungs and other organs where they grow to form hydatid cysts containing brood capsules and scolices.
Echinococcosis is most common in liver but also involves the lungs, less commonly brain, kidney, spleen, muscle and soft tissue.
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The larvae enlarge in situ to become cysts which grow silently for years, usually producing no symptoms until they reach a size of 10 cm or more. Because of their size hydatid cysts of the liver often produce hepatomegaly and may lead to obstructive jaundice. Rupture of a cyst may provoke an acute hypersensitivity reaction.
Traumatic rupture of hydatid cysts of abdominal organs results in severe diffuse pain resembling that of peritonitis and ruptured cyst in the lung may cause pneumothorax and empyema. The diagnosis is made by identifying the hydatid cyst. No effective drug has been established for echinococcosis, although mebendazole has shown mixed results. The treatment of choice is surgical removal of the hydatid cyst.
